Aoyama Tadayo served as a bushō during the Sengoku period.  He was a retainer of the Matsudaira clan of Mikawa Province.

The Aoyama clan originated from Kōzuke Province.  In the era of Tadayo’s lineal heir, Aoyama Tadakado, the clan moved from Ōmi Province to the village of Dōdō in the Nukata District of Mikawa and served Matsudaira Hirotada. 

In 1526, when Ise Moritoki invaded Mikawa and attacked Iwatsu Castle, Tadayo obeyed orders from Matsudaira Nagachika to join reinforcements to repel them.  In the era of Matsudaira Nobutada, there was a movement to back Nobutada’s illegitimate son, Matsudaira Nobusada, but Tadayo opposed this camp and Nobutada’s lineal heir, Matsudaira Kiyoyasu, succeeded Nobutada.  In 1536, Kiyoyasu was struck down by a retainer in an event known as the Collapse at Moriyama.  Oda Nobuhide took advantage of the situation to counterattack against the Matsudaira whereupon Tadayo was killed in action at Idano.